The Contractor will concentrate upon the action of human interferon as a prophylactic agent in reducing the incidence of significant viral infections and/or neoplasia following renal transplantation. Investigation of the activation of type-C oncornaviruses, BK papova-viruses or EW viruses following human renal transplantation. Investigation of the expression of type-C oncornaviruses and immune responses to these viruses in humans during normal gestation, oncogenesis or development of systemic lupus erythematosus. Studies of the interaction of primate type-C oncornaviruses or BK papovaviruses with human leukocytes in vitro. The molecular mechanisms underlying the activation of potentially oncogenic type-C oncornaviruses and papovaviruses.